Compressor discharge silencer



April 23, 1940. A. B. wooD COMPRESSOR DISCHARGE SILENGER Filed A u 9,193a w R0 W Na m 2 ATTORNEY Patented Apr. 23, 1940 UNITED STATES2,198,021 oosmutsson mscnamon smmcaa Alfred B. Wood. Chicago, Ill.,alsilnor to The Westinghouse Air Brake Company, Wllmerding, 2a., acorporation of Pennsylvania Application April 9, 1988, Serial No.201,047 3. mm (01. 11:14:)

This invention relates to sound dampeners and more particularly to asound dampener for use in reciprocating machines, such as an .aircompressor or the like.

In the operation of reciprocating air compressors there occursin certaininstallations a noise commonly referred to as "air' ping." This noise isquite often produced in the compressor discharge pipe and in thereservoir to which said pipe is connected.

In the design of modern public conveyances,

such as the new type high speed traction cars i recently introduced inmany large cities, the comfort of the passengers is considered of majorimportance. It will therefore be evident that any noise due tocompressor operation, such as that above described, will beobjectionable as disturbing to passengers,

The principal object of the present invention is to provide improvedmeans for dampening or absorbing noises of this type produced by an aircompressor.

This object is attained by the provision of a noisedampening or soundabsorbing device connected to the compressor discharge conduit, preferably close to the compressor, which arrange- .ment in practice hasbeen found to substantially eliminate or dampen the noise abovedescribed.

This noise dampening or sound absorbing device is preferably of the typehaving a movable abutment subject on one side to the pressure of thedischarge line and on the opposite side to the pressure of an adjustablespring. The abutment provided therein is adapted to vibrate inaccordance with the intermittent discharges of fluid from the compressorand presents, therefore, in effect a resilient wall which yields to thepressure surges from the compressor and thereby dampens )r absrbs soundwaves created at the compressor due to intermittent discharges ofcompressed air, or to the striking of the compressor discharge valveupon its seat.

Other objects and advantages of the invention will appear in thefollowing more detailed description thereof.

In the accompanying drawing, Fig. l is a diagrammatic sectional view ofa portion of a fluid compressor system embodying the invention; and Fig.2 is a sectional view of a modified form of dampening device.

As shown in Fig. 1 of the drawing the invention is associated, for thepurpose of illustration, with an aircompressor. The compressor shown maybe of the usual type and may comprise a casing having a cylinder sectionI, in which a compressor piston 2 is operatively mounted.

Secured to the cylinder section i is a cylinder head 8, in which theusual inlet and outlet valves 4 and l are operatively mounted to controlthe necessary inletand outlet connections.

The inlet valve 4 is provided with a fluted stem 5 slidably mounted in abore ,6 in the head 3 and the outlet valve I is contained in a chamber Iin the head, which is connected by a discharge pipe 9, a pipe T It, anda branch pipe Ii to a storage reservoir i2, I

Located preferably close to the compressor, and connected to thedischarge pipe 9 by means of the pipe T ill and a pipe I2, is a noisedampening or sound absorbing device ll.

This noise dampening or sound absorbing device H comprises two casingsections it and i8 and a flexible diaphragm ll clamped at its peripherybetween the two casing sections. on one side of the diaphragm I1 is achamber I! connected to the compressor discharge pipe I! and on theopposite side a chamber I! open to the atmosphere through a port in thecasing section it.

A follower 2| is disposed in chamber it engaging the diaphragm i1 and acoil spring 22 is interposed between said follower 2i and adjusting nut23. The adjusting nut 23 has screw threaded engagement with the casingwhereby the pressure of spring 22 on the diaphragm may be varied to suitthe pressure of fluid supplied by the compressor to chamber l8, as'thispressure may be of different degrees in different installations or underdifferent conditions. The follower is provided with a guide stem 24slidably mounted in a suitable bore 25 provided in the nut 23..

In operation, the reciprocating compressor acts in the usual well knownmanner to eilect intermittent discharges of compressed air into pipe 9,whence it flows through pipe T It, pipe ii into the reservoir l2.

Since the diaphragm chamber it of the noise dampener or sound absorbingdevice is open through pipe 13, pipe T III to pipe 9, and is locatedclose to the compressor, the diaphragm will be flexed in the directionof and against the spring upon the crest of a pressure wave in saidpipe,

ume is varied, which variation in volume acts as a cushion to absorb ordampen sound waves.

It has been found in practice that this structure effectively reducesthe noise in the discharge pipe and reservoir. It has also been found inpractice that this structure eilectively reduces the hammer sound incompressor installations and is most effective when the discharge pipeis as short as possible and when the dampener is connected to the end ofsaid pipe opposite the end connected to the compressor, in which casethe Pipe leading to the reservoir is in the form of a branch pipe, asshown in Fig. 1 of the drawing. This construction is believed to be mosteffective due to the fact that sound and pressure waves tend to travelin a straight line, so that such waves created in the discharge pipe 9travel directly into the dampener and are there dampened, or theiramplitude so reduced, due to the action of the diaphragm, as toeliminate or reduce to a negligible degree the noise in the compressorinstallation.

Fig. 2 shows a modified form of noise dampening or sound absorbingdevice in which chamber I8 is isolated from the atmosphere byelimination of port 20 through the casing section It, and the chamber.l8 and I9 at either side of the diaphragm I! are communicativeiyconnected by means of a port 26 through the diaphragm IT.

This noise dampening or sound absorbing device of Fig. 2 operates in amanner similar to the noise dampener or sound absorbing device shown inFig. 1 and above described, except that the port 26 through thediaphragm I1 connecting chambers I8 and I5 is of such capacity that thepressure flow through said port to chamber I9 from chamber l8, upon anincrease of pressure in the discharge pipes 9 and II from the compressori to chamber I8, is sufliclent to cause diaphragm I! to flex in thedirection of and against the opposing pressure of the spring 22 and ofthe pressure in chamber I8. Upon a decrease of the pressure in chamberIt! the port 25 restricts the return flow of pressure from chamber I9 tochamber I 8, so that the spring 22 will return the diaphragm I! to theposition shown in the accompanying drawing.

From the foregoing it may be seen that the noise dampening device ofFig. 2 functions substantially the same as the noise dampening device ofFig. 1 before described. However, the device of Fig. 2 does not requireadjustment oi nut 23 to control the diaphragm movement, regardless ofvariations in the setting of reservoir pressure carried in differentcompressor installations.

While two illustrative embodiments of the invention have been describedin detail, it is not my intention to limit its scope to theseembodiments or otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

.1. A device for dampening sound vibrations created in a conduit inwhich the pressure of fluid intermittently varies, comprising incombination, a casing, a movable abutment in said casing having at oneside a chamber in communication with said conduit and having at theopposite side a chamber in communication with the atmosphere, means inthe last named chamber for opposing movement of said abutment and meansfor varying the opposing force of the first mentioned means.

2. A device for dampening sound vibrations created in a conduit in whichthe pressure of fluid intermittently varies, comprising in combination,a casing, a movable abutment in said casing having at either side achamber one of which is in communication with said conduit, and meansestablishing communication providing for restricted flow of fluidbetween said chambers.

3. A device for dampening sound vibrations created in a conduit in whichthe pressure of fluid intermittently varies, comprising in combination,a casing, a movable abutment in said casing having at one side a chamberin open communication with said conduit and having at the opposite sidea chamber in restricted communication with said conduit, and additional.means in the last named chamber for opposing movement of said abutment.

ALFRED B. WOOD.

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